Preheat the oven to 180°C/fan 160°C/gas 4, and line a couple of 45cm x 38cm baking trays with baking paper.
Place the egg whites in a bowl and whisk until frothy, then add the sugar and whisk until soft peaks are formed. This will take a good few minutes.
Add the rest of the ingredients, apart from the icing sugar, and mix with a spatula until incorporated.
Cut the dough into 18 pieces, each weighing about 30g, then roll them into balls.
Spread the icing sugar in a tray. Put the balls of dough into the tray, roll them around, then leave them to sit for 10 minutes, to absorb some of the icing sugar. Now carpet-bomb the balls with icing sugar, really packing it on.
Carefully place the sugared amaretti on the prepared baking trays, leaving a little space between them because they will puff out a bit.
Bake for 16 minutes, until golden brown, then take them out and leave them to cool a little. Perfect with an espresso.